Silicon最新文献

In order to overcome the deficiency that chlorinated phosphazene base cannot prepare low-viscosity polysiloxanes, especially low-viscosity polysiloxane fluids containing Si–H bonds, linear chlorinated phosphazene acid was prepared using PCl₅ and NH₄Cl, and its application in the preparation of linear polysiloxanes by condensation reaction and equilibrium polymerization reaction was studied. The effects of the dosage of the catalyst, reaction time, passivator type (MgO, NaHCO₃, Fe₂O₃, MnO₂, CaO, ZnO), and its dosage on the structure and yield of the PDMS oligomers were investigated. NMR, GPC, refractometer, and TGA were used to test the structure and properties of the PDMS oligomer. Compared with commercial PDMS fluid, the PDMS fluid prepared with ZnO as a passivator has better thermal properties. When hydroxyl-terminated linear PDMS with low polymerization degree is used, with the addition of 5 ppm of catalyst and NaHCO₃ as a passivator, α, ω-bistrimethylsiloxy-terminated linear PDMS was obtained by means of the condensation reaction with a yield of 91.1%. Using octamethylcyclotetrasiloxane as the monomer, with the addition of 1000 ppm of catalyst and triethylamine as a passivator, various functionalized PDMSs were obtained with yields ranging from 73.7% to 80.4%. Compared with the equilibrium polymerization reaction, the molecular weight distribution of the PDMS prepared by the hydroxyl condensation reaction is narrower. This work provides a new approach to the synthesis of low-viscosity polysiloxanes, especially those terminated with active functional groups.

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In this study, an investigation has been performed on the glass fiber-vinyl ester composites with varying contents of silane treated white fumed silica at different thermal aging conditions. The main objective of this research work is to explicate the effectiveness of silane treated functional fumed silica on commercially used glass fibre-vinyl ester composite at elevated temperature aging conditions. The fumed silica was treated with 3-Aminopropyltrimethoxysilane (APTMS) and the composites were made by a hand layup principle. The composites were further subjected to temperature aging such as 50 & 60 °C @ 180 days and tested for their mechanical, flammability, and water absorption properties. The results indicate that, despite thermal aging the mechanical properties of the composites is stable, revealing the enhanced silane protection effect on glass fiber and fumed silica. Composite GST21, GST22, and GST23, subjected to thermal aging at 60 °C for 180 days, the tensile and flexural strengths experienced reductions compared to the un-aged specimens. However, the decrease in values is minimal, indicating the resilience of the composites even under harsh aging conditions. Flammability tests revealed consistent UL 94 ratings for all specimens, even after thermal aging. Water absorption percentages marginally increased after thermal aging, particularly at higher temperatures, yet remained within acceptable limits. SEM analysis provided visual evidence of the composite's microstructure, highlighting areas of voids, crack formations and low fiber pull-out. Despite some indications of degradation, the overall integrity of the composites remained sound, emphasizing the effectiveness of silane treatment on glass fiber and fumed silica in maintaining structural stability.In summary, while some minor losses in mechanical and physical properties were observed in the thermally aged specimens, the silane treated glass fiber and fumed silica mitigated these effects, ensuring that the composites retained their essential characteristics. Overall, the study underscores the importance of silane barrier protection on the reinforcement materials in enhancing the durability and performance of composite materials, even under challenging conditions.

Developing materials that possess both excellent electromagnetic wave absorption performance and good mechanical properties is crucial for meeting the demands of the military environment. In this study, the carbon fiber reinforced mullite (C_f/mullite) composites were prepared using T300 carbon fiber as the starting material, along with a mixture of alumina sol and silica sol. The C_f/mullite composites exhibited good electromagnetic wave absorption performance under temperature treatment conditions of 700℃ and had a lower dielectric constant, which achieved a minimum reflection loss of -14.28 dB at 1.90 mm, corresponding to a frequency of 17.12 GHz. Additionally, it demonstrated a maximum effective absorption bandwidth of 3.61 GHz at a thickness of 2.10 mm. To meet the mechanical performance requirements under high-temperature conditions, the composites attained a maximum compressive strength of 292.19 MPa under treatment conditions of 500℃. This study provides insights into material selection for future aircraft, particularly in high-temperature and radar detection environments.

In this work, BaTiO₃ nanoparticles synthesized by laser ablation were embedded in p-type and n-type porous silicon (PSi), which were prepared using an electrochemical etching method. Structural analysis confirmed that the synthesized BaTiO₃ nanoparticles are crystalline with a tetragonal structure. The direct optical energy gap of the BaTiO₃ nanoparticles was found to be 3.75 eV at room temperature. Scanning electron microscopy revealed that the synthesized BaTiO₃ nanoparticles have a spherical morphology with an average particle size of 34 nm. The optoelectronic properties of BaTiO₃-embedded n-type and p-type porous silicon photodetectors were investigated, including dark and illuminated current–voltage characteristics, responsivity, external quantum efficiency, and specific detectivity. The responsivity of n-BaTiO₃-embedded p-PSi and n-BaTiO₃- embedded n-PSi was 0.44 and 0.12 A/W at 350 nm, respectively. Energy band diagrams under illumination conditions were constructed for n-BaTiO₃-embedded p-PSi and n-BaTiO₃- embedded n-PSi heterojunction photodetector.

Solar energy has emerged as a promising renewable solution, with cadmium telluride (CdTe) solar cells leading the way due to their high efficiency and cost-effectiveness. This study examines the performance of CdTe solar cells enhanced by incorporating silicon thin films (20-40 nm) fabricated via a sol-gel process. The resulting solar cells underwent comprehensive performance evaluations, including electrical, optical, and structural analyses. The structural behaviour of silicon/CdTe solar cells was investigated using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) techniques. SEM provides a high-resolution analysis of surface morphology with a fine grain of silicon, leads to enhanced functional performance, and XRD confirm the crystalline phase of CdTe and silicon. The study measured and compared key performance metrics, including electrical conductivity, hall coefficient, Tanu plot performance, I-V measurement, rectification ratio, and quantum efficiency with conventional CdTe solar cells. With nano SiC thin layer of 40 nm influences better electrical conductivity (10x10^-2 S/cm), limited hall coefficient (0.0044 cm³/C), with optimum bang gap of 1.45 eV, increased rectification ratio (2 at 0.8 V), and optimum I-V ranges of 1-2. The quantum efficiency of the CdTe: Si solar cell reached 89%, and the rectification ratio increased gradually due to the influence of Si doping. The experimental results show a notable enhancement in photoelectric conversion efficiency with silicon thin films, underscoring their promising potential for future photovoltaic applications.

This research aimed to isolate Staphylococcus ureilyticus MV-1 bacteria and evaluate their potential for soil application. These bacteria can solubilize silicate minerals up to 25 µg/mL in the first 10 h utilizing magnesium trisilicate as a silica source. This encourages plant development by generating plant hormones such as indole acetic acid (IAA). The IAA production peaked at 14 µg/mL after 48 h without further supplementation. Further, significant levels of micro- and macro-nutrient uptake were also recorded using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) in grapevine after treating it with MV-1 indicating the availability of nutrients to plants for proper growth and functioning. The results state that MV-1 had a synergistic effect on plant growth and soil fertility.

Apatite structured polycrystalline samples of rare earth manganese silicates, La₄MnSi₃O₁₃ and Y₄MnSi₃O₁₃, were synthesized via ceramic route, and their crystal structure, morphology, dielectric, optical, and luminescence characteristics were thoroughly examined. Rietveld refinements of the X-ray diffraction data and Raman results confirm that both the compounds are formed in single phase, and crystallize in hexagonal crystal symmetry. Scanning electron microscopy micrographs show the crystalline nature of the synthesized silicates, and the sizes of the grains are found in submicron range. The dielectric constant and tanδ show systematic variation with frequency. The low values of tanδ of these ceramic samples suggest the potential use in energy storage capacitive devices. The calculated wide band gap energies (4.3 eV and 4.03 eV) of these new compositions of silicate apatites make them useful for better absorption and emission of UV light for applications in solid state lighting devices. The photoluminescence characteristics of La₄MnSi₃O₁₃ and Y₄MnSi₃O₁₃ samples make them beautiful sources of green-yellow and green emissions, respectively.

In this paper, we compute the first Zagreb temperature entropy, the second Zagreb temperature entropy, the sum-connectivity temperature entropy, and the product-connectivity temperature entropy of the silicate network. We find the relationship between the temperature entropies of the silicate network. We also analyze and compare the different regressions of these entropies and try to find the best one for each case.

The intent of the proposed research is to analyze the effect of Silicon Nitride (Si₃N₄) and synthesized Graphene Oxide (GO) on the physical, wear and corrosive characteristics of the copper. The copper hybrid composite having constant GO and varying weight % of Si₃N₄ is prepared through powder metallurgy. The GO is synthesized from graphite through modified hummers method and its formation is confirmed through SEM, XRD, Raman and FTIR analysis. The SEM analysis of developed Cu/0.3rGO/xSi₃N₄ confirms the presence of reinforcements and density analysis confirms the reduction density. The microhardness is found increasing with GO and Si₃N₄ addition. Wear rate of the copper found decreases with reinforcement addition due to self-lubricating nature of GO and hardness of Si₃N₄ ceramic. Worn surface confirms the transition of severe wear to mild wear with Si₃N₄ addition. The corrosion results suggest that the composite reinforced with 0.3% GO and 15% Si₃N₄ yielded better corrosion resistance than the other developed composites. Corroded surface analysis confirms the reduction in surface damage with reinforcement addition that shows increase in corrosion resistance of copper with hybrid reinforcement addition.

Here, the capacities of Si₇₂, C₇₂ and B₃₆P₃₆ nanocages as electrodes various types of batteries are investigated by theoretical models. The effects of water and halogen adoption on capacities of Si₇₂, C₇₂ and B₃₆P₃₆ nanocages as electrodes various types of batteries are examined. Results have shown that the V_cell values of Si₇₂, Cl-Si₇₂, Br-Si₇₂, C₇₂, Cl-C₇₂, Br-C₇₂, B₃₆P₃₆, Cl-B₃₆P₃₆, Br-B₃₆P₃₆ nanocages in Mg-ion batteries are 3.58, 3.65, 3.68, 3.81, 3.88, 3.91, 4.05, 4.12 and 4.16 V, respectively. The C_theory values of Si₇₂, Cl-Si₇₂, Br-Si₇₂, C₇₂, Cl-C₇₂, Br-C₇₂, B₃₆P₃₆, Cl-B₃₆P₃₆, Br-B₃₆P₃₆ nanocages as anodes in Mg-ion batteries are 896, 910, 919, 953, 969, 978, 1013, 1031 and 1040 mAhg⁻¹, respectively. The BP nanocages and their halogen doped derivatives have higher V_cell and C_theory than corresponding other studied nanocages. Finally, the Cl-B₃₆P₃₆ and Br-B₃₆P₃₆ nanocages are suggested as new materials as anodes in batteries with acceptable performances.